The present invention concerns apparatuses and methods for transdermal delivery or transport of therapeutic agents, typically through iontophoresis. Herein the terms "iontophoresis" and "iontophoretic" are used to refer to methods and apparatus for transdermal delivery of therapeutic agents, whether charged or uncharged, by means of an applied electromotive force to an agent-containing reservoir. The particular therapeutic agent to be delivered may be completely charged (i.e., 100% ionized), completely uncharged, or partly charged and partly uncharged. The therapeutic agent or species may be delivered by electromigration, electroosmosis or a combination of the two. Electroosmosis has also been referred to as electrohydrokinesis, electro-convection, and electrically-induced osmosis. In general, electroosmosis of a therapeutic species into a tissue results from the migration of solvent, in which the species is contained, as a result of the application of electromotive force to the therapeutic species reservoir.
As used herein, the terms "iontophoresis" and "iontophoretic" refer to (1) the delivery of charged drugs or agents by electromigration, (2) the delivery of uncharged drugs or agents by the process of electroosmosis, (3) the delivery of charged drugs or agents by the combined processes of electromigration and electroosmosis, and/or (4) the delivery of a mixture of charged and uncharged drugs or agents by the combined processes of electromigration and electroosmosis.
Iontophoretic devices have been known since the early 1900's. British patent specification No. 410,009 (1934) describes an iontophoretic device which overcame one of the disadvantages of such early devices known to the art at that time, namely the requirement of a special low tension (low voltage) source of current. That current requirement meant that the patient needed to be immobilized near the current source. The device of that British specification was made by forming a galvanic cell from the electrodes and the material containing the medicament or drug to be transdermally delivered. The galvanic cell produced the current necessary for iontophoretically delivering the medicament. This portable device thus permitted iontophoretic drug delivery with substantially less interference with the patient's daily activities.
More recently, a number of United States patents have issued in the iontophoresis field, indicating a renewed interest in this mode of drug delivery. For example, Vernon et al. U.S. Pat. No. 3,991,755; Jacobsen et al. U.S. Pat. No. 4,141,359; Wilson U.S. Pat. No. 4,398,545; and Jacobsen U.S. Pat. No. 4,250,878 disclose examples of iontophoretic devices and some applications thereof. The iontophoresis process has been found to be useful in the transdermal administration of medicaments or drugs including lidocaine hydrochloride, hydrocortisone, fluoride, penicillin, dexamethasone sodium phosphate and many other drugs. Perhaps the most common use of iontophoresis is in diagnosing cystic fibrosis by delivering pilocarpine. Iontophoretically delivered pilocarpine stimulates sweat production, the sweat is collected, and is analyzed for its chloride ion content. Chloride ion concentration in excess of certain limits suggests the possible presence of the disease.
In presently known iontophoresis devices, at least two electrodes are used. Both of these electrodes are disposed so as to be in intimate electrical contact with some portion of the skin of the body. One electrode, called the active or donor electrode, is the electrode from which the ionic substance, agent, medicament, drug precursor or drug is delivered into the body via the skin by iontophoresis. The other electrode, called the counter or return electrode, serves to close the electrical circuit through the body. In conjunction with the patient's skin contacted by the electrodes, the circuit is completed by connection of the electrodes to a source of electrical energy, e.g., a battery. For example, if the ionic substance to be driven into the body is positively charged, then the anode will be the active electrode and the cathode will serve to complete the circuit. If the ionic substance to be delivered is relatively negatively charged, then the cathodic electrode will be the active electrode and the anodic electrode will be the counter electrode.
Alternatively, both the anode and the cathode may be used to deliver drugs of appropriate charge into the body. In such a case, both electrodes are considered to be active or donor electrodes. For example, the anodic electrode can drive positively charged substances into the body while the cathodic electrode can drive negatively charged substances into the body.
Furthermore, existing iontophoresis devices generally require a reservoir or source of the ionized or ionizable species (or a precursor of such species) which is to be iontophoretically delivered or introduced into the body. Examples of such reservoirs or sources of ionized or ionizable species include a pouch as described in the previously mentioned Jacobsen U.S. Pat. No. 4,250,878, a pre-formed gel body as disclosed in Webster U.S. Pat. No. 4,382,529 and a generally conical or domed molding of Sanderson et al., U.S. Pat. No. 4,722,726. Such drug reservoirs are electrically connected to the anode or to the cathode of an iontophoresis device to provide a fixed or renewable source of one or more desired species or agents.
Recently, the transdermal delivery of peptides and proteins, including genetically engineered proteins, by iontophoresis, has received increasing attention. Generally speaking, peptides and proteins being considered for transdermal or transmucosal delivery have a molecular weight in the range of greater than about 500 Daltons to a molecular weight of 40,000 Daltons (or more). These high molecular weight substances are usually too large to diffuse passively (i.e., without electromotive force) through skin at therapeutically effective rates. Since many peptides and proteins carry either a net positive or net negative charge and because of their inability to diffuse passively through skin at therapeutically useful rates, they are considered likely candidates for iontophoretic delivery as defined herein.
Several approaches have been used to couple or to connect components of an iontophoresis apparatus such as the circuitry to the electrodes. One approach has been to employ a two-sided circuit board. A two-sided circuit board uses connective, conductive conduits or "through holes" to connect the two circuits through the non-conductive circuit substrate or circuit board. The output terminals of the underside circuit then would be in physical and electrical contact with the remaining components of the device. Producing a two-sided circuit board with connective conduits is relatively costly.
Another approach has been to use a single-sided circuit assembly or board and folding the output terminals under the main part of the circuit to create a device configuration that is a flattened circle (with a segment of the circle at its bottom missing) in section. Again this permits physical contact between the circuit output terminals and the rest of the device, (e.g., the electrodes). This approach tends to produce stress points at the folds which can cause the circuit to separate.
Electrotransport devices having elaborate circuitry have also been suggested in the art. Such devices, to date, have been thought of as too costly for utilization in a disposable electrotransport device.
From a commercial standpoint, it is generally desirable for an iontophoresis apparatus to be manufacturable in a cost effective manner, preferably in large quantities. This invention provides apparatuses and methods of manufacture capable of achieving both objectives.